1. Field of the Invention
The present invention relates to an optical switch which can be used, for example, as an access coupler to a series bus.
2. Description of the Prior Art
An access coupler to a series bus is a system that permits picking up or injecting an optical signal in the line of a series bus so as to cause different terminals to communicate with one another. In the event of a terminal breakdown it must be possible to isolate the latter without thereby interrupting the line of the series bus.
French patent application No. 2,538,127 discloses an access coupler to a series bus with four branches, each one having means to receive or transmit light rays and a return device having two operating states. In its first state the return device reflects, and can return, the light between a first and a second branch on the one hand as well as between a third and a fourth branch on the other hand. In its second state the device passes light between the first and the fourth branch on the one hand as well as between the second and the third branch on the other hand. The return device, according to a first variation, is a removable mirror mounted on a support, mobile in translation between two positions: a first position in which the mirror is placed in the path of the light rays, and a second position for which the passage of the light rays is assured by two openings formed in the support. According to a second variation, the return device is a fixed mirror having the said operating states under the influence of a command device.
Although generally satisfactory, this access coupler has a number of disadvantages. Its response time in case of a terminal breakdown is not negligible. The same is true for insertion losses. The cross-talk between branches is not high enough. It would be desirable to provide a coupler which did not have these drawbacks.